1. Field of the Invention
The invention relates to magnetic resonance imaging, and more particularly to a rapid process for producing three-dimensional magnetic resonance imaging.
2. Description Of The Prior Art
Magnetic resonance imaging (MRI) is a non-invasive medical diagnostic imaging modality that can produce high-contrast tomographic images of the interior soft-tissue structures of the human body without the use of ionizing radiation. In many imaging applications, MRI has replaced the competing technology of X-ray computed tomography (CT) as the imaging method of choice. For an MRI examination, the subject is placed in a very strong static magnetic field, and the information necessary to create the images is generated using a series of magnetic field gradient pulses and radio-frequency (RF) pulses. The exact manner in which the gradient and RF pulses are applied is called the pulse sequence. By changing the pulse sequence, the relative appearance of different tissues and pathologies can be changed. Thus, the pulse sequence can be optimized to highlight certain pathological conditions, and even to create images of flow. There are literally an infinite number of possible pulse sequences. The potential variety of pulse sequences and the ability of different pulse sequences to produce images which highlight different types of information are major advantages of MRI compared to other techniques. Critical to the success and acceptance of MRI as a primary imaging modality has been the continued development of new pulse sequence techniques which have both improved the imaging capabilities in existing areas of clinical use and provided new clinical areas of application.
The importance of rapid imaging techniques is discussed in the Manual of Clinical Magnetic Resonance Imaging, (CMRI) by Heiken et al., Raven Press, New York, 1991. It is therein explained that the impetus for the development of rapid imaging techniques has been primarily twofold: to improve the efficiency of clinical MRI and to decrease artifacts that arise from cardiac, respiratory, and other patient motion. The synopsis of the more important rapid imaging techniques discussed in CMRI, at pages 24 through 39, is incorporated herein by reference, as though set forth in detail. At page 31, it is noted that steady state GE images with short TRs and low flip angles provide a myelogram effect in which the spinal cord can be easily differentiated from surrounding CSF.